The invention relates to a calculator or other small battery operated, keyboard actuated electronic device, and particularly to a technique for providing a push-button keyboard ON-OFF switch for such devices.
Electronic calculator systems of the type having all of the main electronic functions within a single large scale integrated (LSI) semiconductor chip, or a small number of chips, are described in the following prior applications or patents assigned to Texas Instruments Incorporated: U.S. Pat. No. 3,819,921, by Kilby, Merryman and Van Tassel, for "Miniature Electronic Calculator", based on an application origninally filed Sept. 29, 1967; Ser. No. 163,565, filed July 19, 1971, now abandoned, by Boone and Cochran, for "Variable Function Programmed Calculator" (now U.S. Ser. No. 420,999, filed Dec. 3, 1973); U.S. Pat. No. 3,892,957, issued July 1, 1975 to John D. Bryant; U.S. Pat. No. 3,987,416, issued Oct. 19, 1976, filed Sept. 24, 1973, by Vandierendonck, Fisher and Hartsell for "Electronic Calculator with Display And Keyboard Scanning"; U.S. Pat. No. 3,900,722, issued Aug. 19, 1975 to Michael J. Cochran and Charles P. Grant, for "Multi-Chip Calculator System"; U.S. Pat. No. 3,991,305, issued Nov. 9, 1976, filed Nov. 19, 1974, by Raymond and Caudel, for "Electronic Calculator or Digital Processor Chip With Multiple Code Combinations of Display And Keyboard Scan Outputs"; and others.
These prior inventions have made possible vast reductions in cost and size, and increase in functions, in electronic calculators. Many millions of such calculators have been produced. The efforts to reduce manufacturing costs, while at the same time to increase the functions available to the user, are continuing. These efforts have resulted in the price of a basic four function electronic calculator dropping from over $200 to less than $10 in less than three years.
Although the MOS/LSI calculator systems as referred to above incorporated in one or two chips all of the computational circuits of the calculator, including data registers, arithmetic unit, a ROM for containing the program, and all of the control circuits, input/output decoders, and the like, it was necessary to have certain devices in addition to the MOS/LSI chip on the printed circuit board to provide a completed calculator. That is, in early versions the MOS/LSI package, along with a display and a keyboard, did not alone provide a calculator. Initially, hand-held, battery operated "one-chip" calculators required, in addition to the MOS/LSI chip, several external circuits for power supply, clock generators, and digit and segment drivers. Subsequent developments made it possible to eliminate the external clock generator circuits by placing these on the chip itself. Also, by using improved MOS processes, it became possible to eliminate or minimize the external power supply circuitry; if the MOS logic could be operated at low voltage, then the chip could be driven directly from the single 9V. battery, for example. The digit and segment drivers were eliminated by improved processes and by the segment scanning technique of copending applications U.S. Pat. Nos. 4,014,013 and 4,014,012, issued Mar. 22, 1977, filed Apr. 7, 1975 and assigned to Texas Instruments. Thus the calculator was reduced to a very few parts, e.g., an MOS/LSI chip, a display device, a keyboard, a printed circuit board, a battery, and a case or housing, in addition to a slide-type ON-OFF switch. The parts and assembly costs for such a calculator, retailing for under $10, would be probably less than $5; in such a situation, the ON-OFF switch becomes a significant cost factor, which was not true when the cost was much higher.
Push-button or keyboard ON-OFF arrangements have been previously provided on calculators, particularly a calculator sold by Litronix of Cupertino, Calif. in 1975. However, this device required a number of components external to the MOS/LSI chip to operate, and so the cost saving was minimal, if indeed the cost was not greater.
It is the primary object of this invention to provide a calculator system or the like wherein a momentary push-button or "keyboard" ON-OFF function is provided, with few or no components external to an MOS/LSI chip being needed, other than a display, a keyboard and a battery. Another object is to provide improved ON-OFF circuitry for an electronic calculator or the like.
An additional object is to provide an electronic calculator or other battery operated device of minimum cost and complexity and maximum battery life.